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Ceramic shell and 3d printing

Hello,

I've got in contact with R&R europe and as soon as the weather permits it I'll receive a 5 gal drum of suspendaslurry along with the 4 bags of sand (shipping in thermal containers is just too expansive, I prefer to wait two weeks)!
My intent is to work with 3d printed pieces and make small casts (my furnace has a maximum load of 6 pounds of bronze for now).

I've seen that some of you are also working with 3d printed patterns (David I've seen your videos on youtube if you're aonemarine ?)
And some with ceramic shell.
Maybe some of you have some experience with 3d printing and ceramic shell ?

I've thought about using PLA (easy to print, and apparently it burns out nicely), moldlay (as it's made for that) and clear resin (from formlabs, someone on their forum showed some pictures of a sword guard made this way).

My main concern is the burnout and shell firing.
Is it possible to directly use the 3d prints or is it necessary to use the 3d print to mold a wax pattern ?

For small parts (example of test parts below) is it possible to use a torch to burn the pattern and fire the shell ? (propane torch, weed burner,...) ? Or is a burnout furnace absolutely required ?
I think that I've seen a video of jagboy and a weed burner hitting a ceramic shell, did you used a furnace to fire the shell or only the torch ?

Here is a test I'll be using for casting as it's my model (3d scan of a cat statue), quite easy and smooth and the result should looks nice in bronze (picture on thingiverse is from a print in a metal filled plastic, polished in a tumbler) :http://www.thingiverse.com/thing:1802638
For a first test I'll try something like maybe 2 inch tall ?

What do you think ?

This thread is as much a question thread as my own thoughts and findings.
Hope I can get a nice results with ceramic shell and 3d prints!

Yep, thats me. Ive only done block casting so cant help you on the ceramic shell...
I worry that directly casting pla in ceramic shell may have trouble with the shell cracking. But i know it has been done also.

Thanks David.
If I have too much trouble with direct pla (or moldlay or resin) in ceramic I'll try making wax molds or if I can make a vacuum casting setup I may try block casting.
I think I've read somewhere that pla was less prone to expanding than wax when heated but I'm not sure were or if it wasn't just bullshit.
Have you tried to print and cast with some wax filaments (like moldlay), is it worth trying ?
I'll see

Yup.. Sorry bud, I hit the shells with the flame thrower (weed burner) and then put the shells into a kiln to vitrify the shells. From what I understand, you only have to heat the shells to around 1700 degrees for a short time to complete this process. However, putting them in the 1700degree heat for a couple hours ensures anything thats inside that shell completely burns away.

Might I suggest not to use pla. Instead print with abs and pour acetone in the shells to dissolve a large portion of the printed object. Then put the piece in a kiln and bring up the heat. This I think should keep the ABS from expanding and cracking the shell.

Thanks jagboy for the infos too!
Would a metal bin with a hole with a steel grid on the bottom and kaowool (ceramic blanket) on the sides and cover furnace work for a burnout furnace ?
And what kind of burner would work better for a burnout furnace ?

I was on the phone with a technical from R&R and he advised to preheat the furnace to 1550 F (as plastic patterns can break the shell otherwise as they tend to expand more and take more time for burning than wax) and place the shell inside for 2-3 hours for a first test (he also advised to make a few more layers on the shell too to reinforce it).

3d, I'm a little biased now towards the electric pottery kiln after doing my jewelry box in it. It's fast, quick and cheap. Your idea of a makeshift kiln with the kaowool would work and I've seen it done. It won't be that efficient, but who cares if it's only got to run for a few short hours. The burnout will be longer thats for sure over wax. We have a b9c creator down in florida for jewelry work and the resin has a seriously pain in the ass burnout schedule. A pid controller fixed that headache and now works great. With that said, satincast investment in a flask is a way different animal than R&R ceramic shell. A few more layers of shell and MAYBE even some built in wire reinforcement in in your shelling might be necessary too. A simple propane burner is easy and cheap to build. I'd make one of those if you don't go electric. Save the oil burner stuff for melting the metal. ;-)

I'd prefer to go electric too!
But it's a bit more difficult to build one and I don't really like the idea of messing with high voltage...
Of course it would allow a better control of the burnout process and that would be a big advantage...
I'm not decided yet for the furnace but from what I've seen it's harder to build/get an electric one.
The solution would be to find a old/broken one for cheap and to fix it, but it's not that often you find a good deal.

For a first test, I'd like to try this one (picture on thingiverse) : http://www.thingiverse.com/thing:1802638 it was printed with some bronze filled filament (colorfabb bronzefill).
It's a 3d scan I made of a cat statue laying around here. I think it's a pretty easy for a first test, not a lot of details.

Question : can the shell be imerged in water before it's vitrified ?
Because if yes, I could print in PVA that is water soluble. Once the shell is complete, imerge it under water to remove the pattern and then fire.
But it would have to stay in the water for a moment, not just dipped and removed. Would it withstand this ?